CHELSEA'S WEAK FLANKS

LUIZ Felipe Scolari's attacking philosophy sees his full-backs Jose Bosingwa and Ashley Cole play a much more attacking role.

While this enhances Chelsea's firepower up front, it creates weaknesses in defence that Arsenal can exploit.

This is especially so with Jon Obi Mikel's erratic form in the 'Makelele' role recently, and the fact that John Terry would be stretched covering for Branislav Ivanovic in the absence of his regular defensive partner Ricardo Carvalho.

Arsene Wenger will probably unleash Samir Nasri and Aaron Ramsey to exploit the gaps left by Chelsea's overlapping fullbacks. If Theo Walcott is fit he will pose an even greater problem with his speed and skill.

Another worrying factor for Chelsea is their vulnerability when defending set-pieces or crosses.

Terry may be strong in the air, but he cannot be everywhere at once, and his big frame affects his mobility in a crowded box.

Chelsea conceded the equaliser against Bordeaux via a corner, and Bacary Sagna scored against the Blues in a similar fashion too last season, so Arsenal should fancy their chances during set-pieces.

FRENCH DISCONNECTION

WILLIAM Gallas and Mikael Silvestre may both be French, but they do not work well together.

Silvestre has been prone to making mistakes in defence during his time at Manchester United, mistakes that usually lead to goalscoring chances or free-kicks in dangerous positions.

Their understanding is simply not there, and I prefer Kolo Toure to take Silvestre's place if he is fit.

But Gallas has improved, judging from his performance against Dynamo Kiev in midweek.

He seemed more relaxed and able to play his own game in his first game since being relieved of his captaincy.

He even seemed more disciplined, staying in defence and not going forward as much as he did in his last days as Arsenal's skipper.

But put him together with Silvestre and Chelsea's Nicolas Anelka will have a field day in attack, given the latter's white-hot scoring form this season.

SUMMARY

DEFENCE is the key in tonight's clash.

Chelsea's defence has not been as watertight in recent days, with a particular vulnerability in dealing with crosses.

Terry could be stretched to the limit covering for his full-backs and an inexperienced Ivanovic.

Gallas' performance against Dynamo Kiev is reassuring, given Arsenal's recent form. But a Gallas-Silvestre central defence pairing would prove shaky against an in-form Anelka.